1. Field of the Invention
The present invention relates to an output apparatus such as an inkjet printer or facsimile machine. More particularly, the invention concerns a device for use in a thermal-compression type fluid jet apparatus employed in a printer head, the device being adapted to prevent back-flow of ink. In addition, the invention concerns a method of preventing back-flow of ink by using the foregoing apparatus.
2. Description of the Related Art
Generally, a fluid jet apparatus employed in a printer head of an output apparatus, such as an inkjet printer or a facsimile machine, ejects ink from an ink chamber outward through a nozzle by exerting physical force to the ink chamber. Such a fluid jet apparatus may be of a thermal type, a piezoelectric type, or a thermal-compression type, depending on the method of exerting physical force on the fluid. This invention concerns the thermal-compression type of apparatus.
An example of a known thermal-compression type fluid jet apparatus is shown in FIG. 1. The fluid jetting apparatus includes a driving module 20, a membrane 30, and a nozzle module 40.
The driving module 20 includes a substrate 15, an oxide film 14 laminated onto substrate 15, a working fluid barrier 25 having a working fluid chamber 27, a heater 16 located in working fluid chamber 27, and a conductor 17 connected with the heater 16.
Nozzle module 40 includes an ink chamber barrier 45 having an ink chamber 57, and a nozzle plate 47 connected with the upper portion of ink chamber barrier 45. On the upper side of nozzle plate 47, a nozzle hole 49 is formed to permit ink in the ink chamber 57 to be forced therethrough as a jet.
Membrane 30 is disposed between ink chamber barrier 45 and working fluid barrier 25. Membrane 30 serves as a partition between the working fluid chamber and ink chamber 57.
The working fluid (such as a heptane or the like) is charged in working fluid chamber 27, while the ink is constantly fed into ink chamber 57 from an ink source (not shown in the drawings).
As electricity is applied to conductor 17, heat is generated by heater 16, and the working fluid in working fluid chamber 27 is heated, forming bubbles. The bubbles increase the pressure in working fluid chamber 27. Accordingly, membrane 30 is upwardly bent, imposing pressure on the ink in ink chamber 57. Accordingly, the ink in ink chamber 57 is forced through the nozzle holes 49.
The conventional fluid jet apparatus, however, has shortcomings. First, it requires a complicated manufacturing process: first, a working fluid preparing process; second, a working fluid charging process; and third, sealing process. Further, since the organic solvent employed as the working fluid (e.g., such as a heptane) is apt to evaporate easily, there is a high possibility of having a space in the working fluid chamber. Once a space is formed in the working fluid chamber, the pressure exerted on the membrane can become insufficient during the heating operation of the heater, so that the quantity of jetted ink can not be precisely controlled.
In order to solve the above-described shortcoming of the prior art, the present inventor has disclosed an ink jet apparatus using ink as the working fluid as shown in FIG. 2.
Referring to FIG. 2, a system with a driving module 120, a membrane 130, and a nozzle module 140 is similar to a conventional ink jetting apparatus, as shown in FIG. 1. Accordingly, driving module 120 includes a substrate 115, an oxide film 114, a working fluid barrier 125 forming a working fluid chamber 127, a heater 116, and a conductor 117. Nozzle module 140 includes an ink chamber barrier 145 having an ink chamber 157, and a nozzle plate 147 having a nozzle hole 149.
The ink jet apparatus shown in FIG. 2 has an interconnecting hole 135 formed in membrane 130. The ink is fed into ink chamber 157 from an external ink source (not shown), and also is fed into working fluid chamber 127 through interconnecting hole 135. Accordingly, the ink serves as the working fluid. As heater 116 heats the ink in working fluid chamber 127, bubbles B are produced in working fluid chamber 127, upwardly bending the membrane 130. Accordingly, the ink in ink chamber 157 is pressurized, and the ink is jetted through the nozzle hole 149.
In such a fluid jet apparatus, there is no need to separately prepare the working fluid since the ink is used as the working fluid. Also, there is no need for a sealing process with respect to working fluid chamber 127. Accordingly, some malfunctions of the fluid jet apparatus are prevented.
The above-described fluid jetting apparatus using the ink as the working fluid, however, has the following problems: First, the ink received in working fluid chamber 127 constantly serves as the working fluid. Hence, the temperature in working fluid chamber 127 keeps increasing by the repetitive heating operation of heater 116. Accordingly, the durability of the fluid jetting apparatus is shortened. Further, as the ink is pressured by the expansion of bubbles B, which are produced by the heating operation of heater 116, and as membrane 130 is upwardly bent, a back flow of the ink occurs from working fluid chamber 127 outside of working fluid chamber 127 through interconnecting hole 135. Accordingly, the appropriate quantity of ink may not be maintained in working fluid chamber 127. When the ink is next jetted through nozzle hole 149 by the heating operation of heater 116, the jet pressure of the ink may be decreased. Accordingly, the desired quantity of ink is not jetted, and the print quality deteriorates when performing repetitious printing operations.
Accordingly, an object of the present invention is to provide an improved ink jet apparatus capable of preventing occurrence of temperature increase in the working fluid chamber as a result of use of the ink to serve as the working fluid. A further object is to prevent a back flow of ink into the ink chamber and the working fluid chamber.
The present invention accomplishes the above objects in a thermal-compression type inkjet apparatus having components as described above. These components include a nozzle module having an ink chamber, a nozzle hole for permitting the ink in the ink chamber to be jetted therethrough; a driving module having a working fluid chamber, the driving module having a heater disposed in the working fluid chamber; a membrane serving as a partition between the ink chamber and the working fluid chamber. The membrane in the device of the invention is provided with an ink injecting hole for interconnecting an ink injecting passage through which ink is fed from an external ink source. Also, an interconnecting hole interconnects the working fluid chamber with the ink chamber to permit the ink in the working fluid chamber injected through the ink injecting hole to be fed into the ink chamber. Further, the ink injecting hole and/or the interconnecting hole have neck modules, respectively, for narrowing the ink injecting hole and the interconnecting hole to sizes smaller than the inner diameters of the working fluid chamber and the ink chamber.
According to the present invention, the sizes of the ink injecting hole and the interconnecting hole are narrowed to be smaller than the inner diameters of the places where the ink flows. Therefore, the back flow of ink is prevented during the ink jetting process. Further, since the ink serving as the working fluid is constantly fed into the working fluid chamber, excessive heat in the working fluid chamber is prevented, and the durability of the inkjet apparatus is improved.